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Trim 10 lines. Roger, please revert any of this you disagree with.
svn:r1048
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@ -316,10 +316,10 @@ calls for padding between end users and the head of the
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cascade~\cite{web-mix}. However, it is not demonstrated whether the current
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implementation's padding policy improves anonymity.
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{\bf PipeNet}~\cite{back01, pipenet}, another low-latency design proposed at
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about the same time as Onion Routing, provided
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stronger anonymity at the cost of allowing a single user to shut
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down the network simply by not sending. Systems like {\bf ISDN
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{\bf PipeNet}~\cite{back01, pipenet}, another low-latency design proposed
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around the same time as Onion Routing, gave
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stronger anonymity but allowed a single user to shut
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down the network by not sending. Systems like {\bf ISDN
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mixes}~\cite{isdn-mixes} were designed for other environments with
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different assumptions.
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%XXX please can we fix this sentence to something less demeaning
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@ -340,15 +340,15 @@ These systems are designed primarily for communication between peers,
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although Herbivore users can make external connections by
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requesting a peer to serve as a proxy.
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Systems like {\bf Freedom} and the original Onion Routing build the circuit
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Systems like {\bf Freedom} and the original Onion Routing build circuits
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all at once, using a layered ``onion'' of public-key encrypted messages,
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each layer of which provides a set of session keys and the address of the
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each layer of which provides session keys and the address of the
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next server in the circuit. Tor as described herein, Tarzan, MorphMix,
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{\bf Cebolla}~\cite{cebolla}, and Rennhard's {\bf Anonymity Network}~\cite{anonnet}
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build the circuit
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in stages, extending it one hop at a time.
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build circuits
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in stages, extending them one hop at a time.
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Section~\ref{subsubsec:constructing-a-circuit} describes how this
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approach makes perfect forward secrecy feasible.
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approach enables perfect forward secrecy.
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Circuit-based anonymity designs must choose which protocol layer
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to anonymize. They may choose to intercept IP packets directly, and
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@ -1311,11 +1311,13 @@ itself may be hostile). While filtering content is not a primary goal
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of Onion Routing, Tor can directly use Privoxy and related
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filtering services to anonymize application data streams.
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\emph{Option distinguishability.} We allow clients to choose local
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\emph{Option distinguishability.} We allow clients to choose
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configuration options. For example, clients concerned about request
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linkability should rotate circuits more often than those concerned
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about traceability. There is economic incentive to attract users by
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allowing this choice; but at the same time, a set of clients who are
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about traceability. Allowing choice may attract users with different
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%There is economic incentive to attract users by
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%allowing this choice;
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needs; but clients who are
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in the minority may lose more anonymity by appearing distinct than they
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gain by optimizing their behavior~\cite{econymics}.
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@ -1558,7 +1560,7 @@ all its CPU time in AES, which is fast. Current latency is attributable
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to two factors. First, network latency is critical: we are
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intentionally bouncing traffic around the world several times. Second,
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our end-to-end congestion control algorithm focuses on protecting
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volunteer servers from accidental DoS rather than optimizing
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volunteer servers from accidental DoS rather than on optimizing
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performance. % Right now the first $500 \times 500\mbox{B}=250\mbox{KB}$
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%of the stream arrives
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%quickly, and after that throughput depends on the rate that \emph{relay
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@ -1819,8 +1821,10 @@ our overall usability.
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In this appendix we provide more specifics about the rendezvous points
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of Section~\ref{subsec:rendezvous}. We also describe integration
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issues, related work, and how well the rendezvous point design
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withstands various attacks.
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issues and related work.
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%, and how well the rendezvous point design
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%withstands various attacks.
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% (Not any more; it's currently commented out. -NM)
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\SubSection{Rendezvous protocol overview}
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@ -1841,9 +1845,9 @@ application integration is described more fully below.
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rendezvous cookie to recognize Bob.
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\item Alice opens an anonymous stream to one of Bob's introduction
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points, and gives it a message (encrypted to Bob's public key)
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that tells him
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about herself, her chosen RP and the rendezvous cookie, and the
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first half of a DH
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telling it about herself,
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her RP and rendezvous cookie, and the
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start of a DH
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handshake. The introduction point sends the message to Bob.
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\item If Bob wants to talk to Alice, he builds a circuit to Alice's
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RP and sends the rendezvous cookie, the second half of the DH
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@ -1853,8 +1857,8 @@ application integration is described more fully below.
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shares the key only with Bob.
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\item The RP connects Alice's circuit to Bob's. Note that RP can't
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recognize Alice, Bob, or the data they transmit.
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\item Alice now sends a \emph{relay begin} cell along the circuit. It
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arrives at Bob's onion proxy. Bob's onion proxy connects to Bob's
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\item Alice sends a \emph{relay begin} cell along the circuit. It
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arrives at Bob's OP, which connects to Bob's
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webserver.
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\item An anonymous stream has been established, and Alice and Bob
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communicate as normal.
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@ -1890,11 +1894,11 @@ introduction connections open or risking such an attack. In this case,
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he can provide selected users
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with a current list and/or future schedule of introduction points that
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are not advertised in the DHT\@. This is most likely to be practical
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if there is a relatively stable and large group of introduction points
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if there is a stable and large group of introduction points
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available. Alternatively, Bob could give secret public keys
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to selected users for consulting the DHT\@. All of these approaches
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have the advantage of limiting exposure even when
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some of the selected high-priority users collude in the DoS\@.
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some of the selected users collude in the DoS\@.
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\SubSection{Integration with user applications}
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